Production of coker feedstocks

ABSTRACT

Coker feedstocks having minimum amounts of sulfur or metals are produced from residuum feeds using an ebullated bed reaction zone. The qualities of the coker feedstocks are controlled through the use of selected operating conditions within the limits of converting 30 to 60 percent of the material in the feed boiling above 975* F to lighter boiling products.

United States Patent Nongbri et al.

1 Nov. 20, 1973 PRODUCTION OF COKER FEEDSTOCKS Inventors: GovanonNongbri, Trenton;

Seymour B. Alpert, Princeton; Ronald H. Wolk, Lawrence Twp., MercerCounty, all of NJ.

Hydrocarbon Research, Inc., New York, N.Y.

Filed: Mar. 15, 1971 Appl. No.: 124,059

Assignee:

US. Cl. 208/50, 208/58, 208/89, 208/102, 208/156, 208/212, 208/216,

Int. Cl C10b 55/00, ClOg 23/02 Field of Search 208/89, 50, 58, 212,208/216, 251 H References Cited UNITED STATES PATENTS 8/1972 Roselius208/50 3,705,849 12/1972 Alpert et al 208/59 3,496,099 2/1970 Bridge208/251 2,871,182 1/1959 Weekman..... 208/50 2,963,416 12/1960 Ward eta1. 208/50 3,418,234 12/1968 Chervenak et al... 208/59 3,412,010 11/1968Alpert et a1 208/112 3,623,974 11/1971 Mounce et a1 208/97 PrimaryExaminer-Delbert E. Gantz Assistant ExaminerG. E. SchmitkonsAtt0rney--Nathaniel Ely and Bruce E. l-losmer [5 7 ABSTRACT 3 Claims, 3Drawing Figures PAIENIEDnnveo ms 3.' 773L653 snmlnFz' P IT 2| k W 2 I3 QFIG. I

Relotive Reoc'ror Volumes Conversion of 975+ Material in the FeedINVENTORS v GOVANON NONGBRI 2 SEYMOUR B.ALPERT RONALD H. WOLK RNEYPAIENIEIJNUVZO ms 3373.653

- sumac; 2

Vol /0 Converslon of 975F Material in the Feed FIG. 3

INVENTORS GOVANON NONGBRI SEYMOUR B.ALPERT RONALD H.WOLK

A RNEY PRODUCTION OF COKER FEEDSTOCKS BACKGROUND With a large increasein light hydrocarbon product demand in the United States, the petroleumrefiner has had to increase his throughput rate. As a result, he isfaced with the problem of discarding the increased residual fractionswhich arise from refining more crude. Elimination of residuals has beenthe subject of considerable study by the refining industry. This has ledto a substantial investment in processing facilities which provide awide variety of approaches to the solution of this problem. Among theseveral processes either currently in operation or being installed are:

1. coking (both delayed and fluid) 2. propane deasphalting 3. partialoxidation 4. residue hydrocracking; and

5 residue desulfurization.

US. Pat. No. 2,871,182 discloses one method of making coke from long andshort residua. This patent like other prior art teachings fails to solvethe problem of how to produce a coke with minimum levels of metals orsulfur or how to handle the increased volume of residua withoutrequiring increased coker units. The metals and sulfur content of thecoke produced is dependent upon the characteristics of the cokerfeedstocks. In todays ecology oriented society, the restriction ofpollutants such as sulfur and metals in fuel sources poses a situationthat requires new methods by which fuels, such as coke, can be producedso that they will be low in sulfur and metals. At the same timedifferent consumers require coke having different characteristics. Thisthen leaves one with the task of producing a coker feedstock by a methodwhich will allow one to control the sulfur and metals levels in theproduct. The prior art teaches that there is increased desulfurizationand demetalization of'residua feeds with increased severity ofhydrogenation conditions and conversions. This teaching does not provetrue when producing coker feedstocks from residua feeds.

SUMMARY In this invention it was found that residua feeds could beconverted into coker feedstock having minimum levels of sulfur or metalswhich would enable one to produce coke having specific desiredcharacteristics. It was discovered in the operation of this inventionthat the level of sulfur and metals in a coke and, therefore, in a cokerfeedstock is dependent upon the percent conversion of the fraction inthe feed boiling above 975 F to material boiling below 975 F. It wasfurther discovered that the levels of sulfur and metals in the ebullatedbed reaction zone prior to using it as a feedstock to a coker. Theebullated bed is a three phase reaction zone in which the gas and liquidare passed upwardly through the particulate solids in random motion inthe liquid. The operation of the ebullated bed reaction zone isdisclosed in US. Pat. Re. 25,770.

It was discovered that in the ebullated bed reaction zone the resid ishydrocracked under conditions that can control the resid yield to matchexisting coker capacity. No additional cokers are necessary to handlethe increased residua and operating conditions can be further varied tocontrol the level of sulfur and metals in the coker feed.

A process has been discovered in this invention, wherein coke havingless than 200 ppm vanadium and less than 2.5 percent sulfur can beproduced from the residual fractions discarded in the refining of crudepetroleum. The levels of sulfur and metals, hereinafter referred to asvanadium, vary with the source of the crude which in turn affects thelevels of the sulfur and metals in the resid and, therefore, in thecoker feedstock and the resulting coke.

In this process the minimum sulfur and vanadium that can be present inthe product, coker feedstock, obtained from the hydrotreating of theresid can be determined experimentally for each type of crude. It hasbeen determined that coke with the desired minimized sulfur and vanadiumcontent can be obtained by operating the ebullated bed for thehydrotreating of the resid under pressures between 1,500 and 3,000 psighydrogen partial pressure, temperatures between 700 and 900 F andpreferably 750 to 840 F, a liquid space velocity of 0.3 to 1.5 volumesof feed per hour per volume of reactor, V,/hr/V,, with a suitablehydrotreating catalyst as hereinafter described, and a conversion ofbetween about 30 and about 60 percent of the 975 F plus fraction, in theresid, to lower boiling hydrocarbons. Within these conversionpercentages the minimum of sulfur or vanadium in the product is afunction of the temperature, space velocity, pressure and catalystactivity, i.e., replacement rate.

When the resid is hydrotreated under the above conditions, a'liquideffluent is obtained from the reaction zone which has a 975 F plusfraction with less than 2 percent sulfur and less than ppm vanadium.

The liquid effluent undergoes a separation to provide the cokerfeedstock which will give a coke having the desired range of sulfur andvanadium content.

DESCRIPTION OF THE DRAWING FIG. 1 is a schematic diagram of the processfor producing a coker feedstock from a hydrocarbon residuum.

FIG. 2 shows the change in the level of sulfur in the 975 F+ fractionwith a change in liquid space velocity and H pressure at a given percentconversion of the 975 F+ material in the feed.

FIG. 3 shows the change in the level of vanadium in the 975 F+ fractionwith a change in the liquid space velocity and H pressure at a givenconversion of the 975 F+ material.

DESCRIPTION OF THE PREFERRED EMBODIMENT Generally, the ebullated bedhydrotreating of a hydrocarbon residuum material ,is carried out asdiagrammed in FIG. I and may be described as follows:

The feed material which normally has at least 25 volume percent ofcomponents boiling above about 975 F at 1 together with hydrogen in 5passes in line 3 to reactor 2. Such a reactor will be charged with asuitable catalyst having the required hydrotreating, desulfurization ordemetalization, characteristics. The catalyst particles will have anarrow size distribution with a diameter in the range from about 20 toabout 325 USS mesh. Alternatively, catalysts in the form of extrudatesof about 5% inch to about 1/32 inch diameter may be used.

The catalyst may be of any type of material which can affecthydrogenation of the sulfur and metal compounds in the feed. Particularexamples would be cobalt molybdate on alumina (preferred), nickelmolybdate on alumina, nickel tungstate on alumina, alumina and the likeas defined in the prior art. Normally, the catalyst consists essentiallyof alumina promoted with metals and compounds of metals selected fromgroups Vlb and VIII of the periodic table.

The residuum and hydrogen pass by upflow through the bed of catalystsuch that the bed will tend to expand to at least percent of the restvolume of the bed and such that the catalyst particles are all in randommotion in the liquid. In such condition, they are described asebullated. As stated in the Johanson patent cited hereinabove, one canoperate the particular process so as to cause the mass of contactmaterial in the fluid to become ebullated and to calculate the percentexpansion of the ebullated mass at any given set of reaction conditions.

Under the preferred conditions of temperature, and pressure set forth, atotal effluent is removed in l l and passes with hydrogen in 7 through 9to reactor 4 for further hydrogenation in an ebullated bed under thepreferred operating conditions of reactor 2. Reactor 4 will also containa suitable catalyst as hereinbefore described. The conversion of the 975F plus fraction in the resid feed by the hydrotreating process isbetween 30 and 60 percent.

A vapor overhead effluent is removed in 17 and a liquid effluent isremoved in 13 to separator 6. The liquid effluent coker feedstock in 13has less than 2 percent sulfur and less than 70 ppm vanadium in the 975F plus fraction. An overhead is removed in 21 and the desired coker feedis passed in 25 to coker 10. Coker 10 may be any of several known cokingoperations existing in the art. The 650 F and lighter products from thecoker are removed in 29 while the heavy gas oils leave coker 10 in 33.The coke leaves in 37. It has been found that a two or more stagehydrogenation is preferred although a single stage may be used as well.

FIG. 2 is a graph showing the effect of liquid space velocity andhydrogen pressure on the sulfur content of the 975 F+ fraction in theproduct. Point A represents the sulfur content of the resid feed. Thefeed is subjected to operating conditions under a liquid space velocityin volume of feed per hour per volume of reactor having a value Q and ata hydrogen partial pressure having a value H. Curve B represents thesulfur level in the 975 F+ product fraction when operating with a liquidspace velocity of Q and a hydrogen partial pressure of 0.67 H. Curve Dwas operated at 0.5 Q'and 0.67 H, curve C had operating conditions of Qand H and curve E had operating conditions of 0.5 Q and H. Line F is thelocus of minimum points at a hydrogen partial pressure of H while line Gis the locus of minimums of sulfur in the 975 F+ fraction in the productat 0.67 H.

FIG. 3 is a graph showing the effect of liquid space velocity andhydrogen pressure on the vanadium content of the 975 F+ fraction in theproduct. Point Z represents the vanadium content of the feed. The feedis subjected to operating conditions under a liquid space velocity involume of feed per hour per volume of reactor, having a value 0" and ata hydrogen partial pressure having a value H." Curve X represents thevana- All minimums in FIGS. 2 and3fall between 30 and 60 percentconversion of the 975 F+ material in the feed.

In general, it is envisioned that the reaction conditions utilized inhydrogenation process of this type would be within a temperature rangeof between 700 and 900 F and preferably between 750 F and 840 F, ahydrogen partial pressure range of between 1,500 and 3,000 psig, aliquid space velocity range of between 0.3 and 1.5 V,/hr/V and acatalyst replacement rate between 0.02 and 0.4 lbs/bbl.

It has been found, in accordance with this invention, that bycontrolling the quality, that is to say sulfur, and vanadium content ofthe coker feedstock, that the qual ity of the coke produced therefrom iscontrolled. The quality of the coker feedstock is, in turn, controlledby the operating conditions used in the ebullated bed, hydrogenationreactor and the feedstock characteristics.

In accordance with this invention the necessary quality of the coke isobtained by controlling the quality of the coker feedstock. Variationsof the operating conditions in the ebullated bed hydrotreating reactorsresults in conditions that will produce a coker feedstock with thedesired properties. That is to say, from a given amount of feedstock, aknown coker capacity and coke yield requirements, the desired level ofconversion of the 975 F+ material in the ebullated bed unit is estimatedto thereby produce a coker feedstock that will produce coke having thedesired levels of sulfur and metals.

EXAMPLE I To illustrate the hereinabove disclosure, the following caseson West Texas resids are presented.

In Table I the yields and coke product properties obtained from directcoker processing of virgin vacuum bottoms are given.

The yields and product properties obtained from the ebullated bedhydroconversion processing of the virgin vacuum. bottoms followed by thecoker processing of the ebullated bed pretreated vacuum bottoms cokerfeedstock are summarized in Tables 2 and 3 respectively.

Tables 2 and 3 ,show that if one wanted a coke with about 1.5 percentsulfur and about 140 ppm of vanadium then one would need a cokerfeedstock with about 1.2 percent sulfur and about 41 ppm of vanadium.Starting with a residuum with 2.65 percent sulfur and ppm of vanadiumone would then find that ebullated bed reactor should be operated at 780F, 2250 tained wherein the ebullated bed processing of the cokerfeedstock is performed are lower than those of the coke obtained bydirect coking of the virgin resid; (2) the yield of coke by directcoking of the virgin resid is about percent of the total resid, ascompared to 18.5 percent when processing the virgin resid through theebullated bed reactor prior to coking, thereby reducing the morevaluable lower boiling hydrocarbons obtained from the resid.

depends respectively on the sulfur content and metals content of thecoker feedstock. These are fixed properties of the virgin vacuum residand hence the coke yield and its sulfur and metals contents are definedwhen the virgin vacuum resid is directly coked. On the other hand, theproperties of the coker feedstock are easily changed in the ebullatedbed by manipulating the operating variables. Thus the coke yield and thesulfur and metals contents of the coke can be adjusted to meet Thesulfur and metals contents and the yield of coke 10 with different cokeneeds.

TABLE 1.DIREC'I COKER PROCESSING OF VIRGIN VACUUM RESIDUUM Charge StockWt. perv BPSD API Lb./hour eentS LIL/hr. s

Vacuumreslduum 30,000 10.4 430,000 2.65 11,550

Product Yields and Properties Component Wt. per- Lb./hour cent S BPSDAPI Total.

TABLE 2.EBULLATED BED PROCESSING OF VACUUM RESIDUUM FOR (JOKER FEEDSTOCKFeedstock inspections: 10.4 .API gravity; 2.65 wt. percent sulfur; 92vol. percent; 975 F.+;

70 p.p.m. V; p.p.m. Nl; N2=.629 wt. percent Charge Stocks Wt. per- BPSDAPI LIL/hour cent S Lb./hr. S l Vac. Reslduum 30, 000 10. 4 436, 000 2.11,556 Hydrogen (550 s.e.f./l:.) 3,

Total 439. 600

Process Yields and Product Properties Wt. Vol. Wt. per- Componentpercent percent API LbJhour cent S Lb .lhr. S

2/1 p.p.m. V/Ni. 41/36 p.p.m. V/Ni.

TABLE 3.COKER PROCES SING OF EBULLATED BED TREATED VAC- UUM RESID UUMCharge Stock Wt. per- BPSD API Lb./hour cent S Lb./hr. S

Process Yields and Product Properties Wt. Vol. Wt. per- Componentpercent percent API Lb./hour cent S Lb./lir. S

Total 100. 0 268, 688 3, 224

8 /120 p.p.m. V/Ni.

Although the above example and discussions disclose a preferred mode ofembodiment of this invention, it is recognized that from suchdisclosures, many modifications will now be made obvious to thoseskilled in the art and it is understood, therefore, that this inventionis not limited to only those specific methods, steps or combinations orsequence of method steps described, but covers all equivalent steps ormethods that may fall within the scope of the appended claims.

We claim:

l. in a process for the production of coker feedstocks having minimumamounts of sulfur or metals wherein a petroleum resid, containing atleast 25 percent of hydrocarbons boiling above 975 F, and a hydrogencontaining gas are fed in upflow through an ebullated bed reaction zonewhile maintaining a particulate hydrotreating catalyst in said reactionzone at a hydrogen partial pressure between 1500 and 3000 psi, atemperature between 700 and 900 F and at a space velocity between 0.3and 1.5 V lhr/V wherein the improvement comprises:

a. converting, in said reaction zone, 30 to 60 percent of the fractionboiling above 975 F in the feed to lower boiling fractions;

b. removing a liquid effluent from said reaction zone;

0. and separating, from said liquid effluent, the bottom fractionboiling above 975 F, having less than two weight percent sulfur and lessthan ppm vanadium.

2. The process of claim 1 wherein said liquid effluent removed in stepb) is passed to a second reaction zone, wherein said second reactionzone is operated under conditions substantially the same as the firstreaction zone, before completing step c).

3. The process of claim 2 wherein the reaction zones are operated at atemperature between 750 and 840 F and the catalyst is replaced at a ratebetween 0.02 and 0.4 pounds of catalyst per barrel of resid fed whereinsaid bottom fraction is coked to yield a coke having less than 200 ppmvanadium and less than 2.5

percent sulfur.

2. The process of claim 1 wherein said liquid effluent removed in stepb) is passed to a second reaction zone, wherein said second reactionzone is operated under conditions substantially the same as the firstreaction zone, before completing step c).
 3. The process of claim 2wherein the reaction zones are operated at a temperature between 750*and 840* F and the catalyst is replaced at a rate between 0.02 and 0.4pounds of catalyst per barrel of resid fed wherein said bottom fractionis coked to yield a coke having less than 200 ppm vanadium and less than2.5 percent sulfur.